1. Field of the Invention
This invention relates to a hologram reconstructing apparatus for reconstructing three dimensional images.
2. Related Background Art
Holography is a technique for enabling three dimensional images to be reconstructed by recording and reconstructing the phase and amplitude of light, but since it is necessary to record and reconstruct minute interference fringes formed by a laser beam, a photo-sensitive material of very high resolusion or the like has long been used as a recording medium for said interference fringes and necessarily, reconstructed images have been limited to stationary ones.
In recent years, however, with the advance of science and technology, spatial light modulators (such as liquid crystal optical elements or acousto-optical elements) having high resolusion and quick in response have been developed and the high-speed display of minute interference fringe patterns has become possible and therefore, a number of examples using these to construct a real time hologram (moving image hologram) reconstructing apparatus have come to be seen. Japanese Laid-Open Patent Application No. 1-84993 discloses a real time hologram reconstructing apparatus using a liquid crystal dot matrix display element. FIG. 1 of the accompanying drawings shows the construction of this apparatus. An interference fringe pattern for making the reconstruction of a desired three dimensional image is produced by a microprocessor 65 and an image control apparatus 64 in FIG. 1, and the interference fringe pattern is displayed as a black-and-white pattern on a liquid crystal dot matrix element by a driver circuit 62. If this pattern is illuminated by a laser beam emitted from a laser apparatus 63 and is observed from the direction of arrow A, the observer can observe a three dimensional image. Further, if the interference fringe pattern displayed on the liquid crystal dot matrix element is dynamically changed, a three dimensional moving image can be obtained.
However, the real time hologram reconstructing technique according to the conventional art has suffered from the following problems:
1) The manufacture of such a spatial light modulator of high resolusion which corresponds to a photosensitive material is difficult and the display of too minute an interference fringe pattern cannot be accomplished and further, faithful reconstruction of an intended three dimensional image is impossible, and PA1 2) The amount of information of the interference fringe pattern displayed on the spatial light modulator is too enormous for the ability of a system for calculating and processing the interference fringe pattern to catch up with it.